1. Field of the Invention
The present invention relates to an air breather structure in a transmission.
2. Description of the Prior Art
Japanese Patent Application Laid-open No. S60-215158 discloses a conventional air breather structure in a transmission. As shown in a schematic sectional view in FIG. 2, an air breather chamber S is defined in a transmission case 1 by a partition wall 2, and in the inner part of the air breather chamber S, an air breather pipe 3 is connected from the outside. An internal pressure caused in the transmission is introduced into the air breather chamber S from an entrance 51 of the air breather chamber S, and the internal pressure is released outside through the air breather pipe 3 to prevent the internal pressure in the transmission from increasing. In the conventional air breather structure, when the internal pressure is released outside from the air breather pipe 3 through the air breather chamber S, there is a problem that oil in the transmission enters the air breather chamber S from the entrance 51. Thus, the oil is blown out outside through the air breather pipe 3, and so-called "blow of oil" is generated.
Thereupon, in order to enhance air/liquid separating performance, it seems to be a good idea to increase volume of the air breather chamber S. However, if the volume of the air breather chamber S is increased, the entrance 1 becomes too wide, and the oil can easily enter the air breather chamber S by the flow of the fluid generated by rotation of gear in the transmission case 1. Further, if the oil is concentrated in a direction of the air breather chamber when the automobile is running down a hill, there is a problem that the oil enters the air breather chamber S.